The present disclosure relates to a controller adapted for an internal combustion engine that includes a filter that traps particulate matter in exhaust gas, an EGR passage that connects the upstream side of the filter in the exhaust passage to the intake passage, and an EGR valve that adjusts the cross-sectional flow area of the EGR passage.
For example, Japanese Laid-Open Patent Publication No. 2009-36183 discloses an internal combustion engine that includes a filter that traps particulate matter in exhaust gas, an EGR passage that connects the exhaust passage and the intake passage to each other, and an EGR valve that adjusts the cross-sectional flow area of the EGR passage.
If the amount of particulate matter trapped by the filter increases, the pressure on the upstream side of the filter may become excessively higher than the pressure on the downstream side. When the pressure on the upstream side of the filter is excessively high, the pressure on the upstream side of the EGR valve becomes excessively higher than the pressure on the downstream side. This causes a great amount of exhaust gas for the opening degree of the EGR valve to flow into the intake passage, which may reduce the controllability of the internal combustion engine.